CHEMISTRY GLOSSARY

osmometry    →   osmometrija

Osmometry is a determination of the average molecular weight of a dissolved substance from measurements of osmotic pressure.

oxonium ion    →   oksonijev ion

Oxonuim ion (H₃O⁺) is formed when a molecule of water binds with a proton.

dissociation constant    →   konstanta disocijacije

Dissociation constant is a constant whose numerical value depends on the equilibrium between the undissociated and dissociated forms of a molecule. A higher value indicates greater dissociation.

The term dissociation is also applied to ionisation reactions of acids and bases in water. For example

which is often regarded as a straightforward dissociation into ions

The equilibrium constant of such a dissociation is called the acid dissociation constant or acidity constant, given by

The concentration of water [H₂O] can be taken as constant.

Similarly, for a base, the equilibrium

is also a dissociation; with the base dissociation constant or basicity constant, given by

K_a (K_b) is a measure of the strength of the acid (base).

electronegativity    →   elektronegativnost

Electronegativity is a parameter originally introduced by L. Pauling which describes, on a relative basis, the power of an atom to attract electrons. For example, in hydrogen chloride, the chlorine atom is more electronegative than the hydrogen and the molecule is polar, with a negative charge on the chlorine atom.

There are various ways of assigning values for the electronegativity of an element. Pauling electronegativities are based on bond dissociation energies using a scale in which fluorine, the most electronegative element, has the value 4 and francium, the lowest electronegative element, has the value 0.7.

polar solvent    →   polarno otapalo

Polar solvent is a liquid with polar molecules which dissolves polar compounds, because the charges on the endings of the solvent’s molecules attract the elements from ion crystals.

propagation    →   propagacija

Propagation is the step in a polymerization mechanism, where new monomer molecules are added to the growing polymer chain in the free radical process.

protein    →   bjelančevina

Proteins are natural organic compounds of animal or herbal origin, essential in diet. They are natural polymers developed from a crowd of interconnecting monomers of amino acids, with relative molecular masses amounting up to a few million.

radical    →   radikal

Radical is a reaction intermediate where a bond is broken and the two parts of the molecule exist carrying a single unshared electron. The radicals are normally destroyed quickly by recombination or they break into another radical and a stable molecule.

solution    →   otopina

Solutions are homogeneous mixtures of clean substances. Solutions contain two or more substances mixed in a state of molecular dispersion. Component which is found in solution in greater amount than other components is called a solvent and other components are called dissolved substances. Solution can be unsaturated, saturated and oversaturated.

enantiomer    →   enantiomer

Enantiomers are a chiral molecule and its non-superposable mirror image. The two forms rotate the plane of polarised light by equal amounts in the opposite directions. Also called optical isomers.